Oil and gas well primary separation device

ABSTRACT

A primary separation apparatus for separating natural gas from high pressure, high velocity production streams comprising a liquid dispersion of water, sand, natural gas, and isolation plug cuttings.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. § 119(e) to U.S.Provisional Application Ser. No. 61/813,744 filed Apr. 19, 2013, whichis incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

This invention relates to oil and gas well completion and production.

2. Description of the Prior Art

Geologists have known for years that substantial deposits of oil andnatural gas are trapped in deep shale formations. Around the worldtoday, with modern horizontal drilling techniques and hydraulicfracturing, the trapped oil and natural gas in these shale reservoirs isbeing produced, gathered and distributed to customers.

Initially, a vertical hole is drilled in a formation down to a depthbelow the water table, and steel casing is inserted into the boreholeand cemented in place, thus providing an impermeable barrier between thewater table and borehole. Vertical drilling continues to a depth calledthe “kick-off” point, where the wellbore begins curving to becomehorizontal. One advantage of horizontal drilling is that it is possibleto drill several wells from only one drilling pad, minimizing the impactto the surface environment. When the targeted distance is reached, thedrill pipe is removed from the borehole, and additional steel casing isinserted through the full length of the wellbore and cemented in place.

The drilling rig is then removed and preparations for well completionare then undertaken. The first step is to create a connection betweenthe final casing and the reservoir rock. To do so, a device known as aperforating gun, equipped with shaped explosive charges, is lowered intothe wellbore down to the layer containing oil and/or natural gas. Theperforating gun is then fired, which creates holes through the casing,cement, and into the target reservoir rock. Next, a mixture of water,sand and other chemicals is pumped into the deep underground reservoirformations, which creates fractures in the reservoir rock. A proppingagent, usually sand carried by the high viscosity fluid, is pumped intothe fractures to keep them from closing when the pumping pressure isreleased. This initial stimulation segment is then isolated with aspecially designed plug inserted into the steel casing to seal off theperforated (and thus the fractured reservoir) and prevent productionfrom the isolated section. The perforating gun is then moved to the nextstage of the wellbore to perform the same process, which is thenhydraulically fractured in the same manner. This process is repeatedalong the entire horizontal section of the well, which may extendseveral miles.

Once the stimulation is complete, the isolation plugs are drilled outand production begins. Initially water, and then natural gas or oilflows into the horizontal casing and up the wellbore. In the course ofinitial production of the well, approximately 15 to 50% of thefracturing fluid may be recovered, a process known as “flowback.” Thepurpose of the flowback is to safely recover these substances from thewell and transition the marketable hydrocarbons of the well stream to asales pipeline or storage tank. The fracturing fluid is then eitherrecycled to be used on other fracturing operations or safely disposed ofaccording to government regulations.

The fracturing process described above requires equipment to handle andseparate drilled isolation plug cuttings along with large volumes ofsand, fracturing fluids, and oil and natural gas. The drilled isolationplug cuttings and sand need to be separated to keep from plugging otherfluid clean up and separation equipment, which may cause a loss ofcirculation detrimental to downhole tools. Accordingly, a device isneeded to efficiently separate drilled isolation plug cuttings, sand,fracturing fluids and oil and natural gas during a flowback process ofproduction of fluids from the wellbore.

3. Identification of the Objects of the Invention

An object of the invention is to accomplish one or more of thefollowing: Provide an apparatus for primary separation in frackingoperations that combines isolation plug cutting separation, sandseparation, and gas separation in a single separation assembly.

SUMMARY OF THE INVENTION

In one aspect, embodiments disclosed herein relate to an apparatus forseparating natural gas from high pressure, high velocity productionstreams comprising a liquid dispersion of water, sand, natural gas, andisolation plug cuttings. The apparatus includes a housing having a firstend and a second end, and an interior cavity extending therebetween, andan inlet port disposed at said first end of said housing. A flow sleeveis disposed within said interior cavity of said housing and extendingfrom said first end to said second end of said housing, and a firstscreen is disposed within said flow sleeve and in fluid communicationwith said inlet port. An annulus is formed between an outer diameter ofsaid first screen and an inner diameter of said flow sleeve. A baffle isdisposed within said interior cavity at said second end of said housing,and said baffle is arranged and designed to enhance separation of saidproduction stream into its constituents, a liquid drain in a lowerportion of said housing, a second screen coupled to an upper portion ofsaid housing, and a gas outlet.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated in the accompanying drawings wherein,

FIG. 1A illustrates a cross-section view of a primary separator inaccordance with one or more embodiments of the present disclosure;

FIG. 1B illustrates an enlarged cross-section view of a second end ofthe primary separator of FIG. 1A; and

FIG. 2 the primary separator of FIG. 1A on location.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The aspects, features, and advantages of the invention mentioned aboveare described in more detail by reference to the drawings, wherein likereference numerals represent like elements. FIG. 1 illustrates across-section view of a primary separator 100 in accordance with one ormore embodiments of the present disclosure.

Main Housing

The primary separator 100 includes a generally cylindrical main housing102 having a first flange 104 on a first end and a second flange 106 ona second end. The main housing 102 complies with all PSL-3 NACE H₂Sspecifications. The main housing 102 is rated for pressures of at least5,000 psi, 10,000 psi, 15,000 psi, and up to 20,000 psi. A generallycylindrical interior cavity 108 or bore is formed within the mainhousing 102. An inlet port 110 may be coupled to the main housing 102 byway of a first adaptor 112 that is fastened to the first flange 104 withone or more threaded fasteners 114. One or more valves 116, 118 may bedisposed between the inlet port 110 and adaptor 112. Valves 116, 118 maybe gate valves, either manually or hydraulically operated, or othervalves known to one of ordinary skill in the art for opening or closinginlet port 110 to allow production fluid to enter the primary separator100. Alternatively, inlet port 110 may be fastened directly to the firstflange 104 of the main housing 102. A pressure gauge 137 may be coupledto the inlet port 110 and arranged and designed to monitor pressureentering the inlet port 110.

A second adaptor 120 may be fastened to the second flange 106 of themain housing 102 by way of one or more fasteners (not shown). Further,an end cap 122 may have an internal thread that engages an externalthread of the second adaptor 120 and is threaded thereon. The end cap122 is preferably removable from the second adaptor 120. Alternatively,the end cap 122 may be attached directly to the second flange 106 of themain housing 102 by way of one or more threaded fasteners.

The main housing 102 further includes a top flange 124. A top flowadaptor 126 is disposed within the top flange 124 and secured therein byway of one or more threaded fasteners 128. The top flow adaptor 126 mayhave a flow channel therein that decreases in diameter from a bottomsurface of the flow adaptor to the top surface. One or more sealingmembers 130 may be installed between the top flow adaptor 126 and thetop flange 124.

The main housing 102 also includes a bottom flange 130. A bottom flowadaptor 132 or flow block is disposed within the bottom flange 130 andsecured therein by way of one or more threaded fasteners 134. The bottomflow adaptor 132 may have a flow channel therein that decreases indiameter from a top surface of the flow adaptor to a bottom surface. Oneor more sealing members 136 may be installed between the bottom flowadaptor 132 and the bottom flange 130. The bottom flow adaptor 132includes an outlet port 138 or drain through which fluid or sediment mayflow out of the main housing 102.

Finally, a pressure gauge 139 may be coupled to the main housing 102 andarranged and designed to monitor pressure within the interior cavity 108of the main housing 102.

Plug Cuttings Screen Assembly

A screen assembly 140 is disposed within the interior cavity 108 of themain housing 102. The screen assembly 140 includes a flow sleeve 142that extends within the interior cavity 108 of the main housing from afirst end to a second end of the main housing 102. A first end of theflow sleeve 142 is threaded within the first flange 104 of the mainhousing 102 and abuts the first adaptor 112 coupled to the first flange104. A second end of the flow sleeve 142 is threaded within the secondflange 106 and abuts the second adaptor 120. The flow sleeve 142 ispreferably a hollow cylindrical tube having an inner diameter of atleast about 3 inches, 4 inches, or 5 inches, up to about 6 inches, 7inches or 8 inches. The flow sleeve 142 has one or more ports 145 a and145 b located proximate the second end of the flow sleeve 142, whichallow gas and fluid to exit the flow sleeve 142 and enter the interiorcavity 108 of the main housing 102. As best illustrated in FIG. 1B,upper port 145 a may have a diameter of at least about ½ inch, ¾ inch,or 1 inch, up to about 1½ inches, 1¾ inches, or 2 inches. Lower port 145b may have a diameter of at least about 1½ inches, 2 inches, or 2½inches, up to about 3 inches or 4 inches.

A screen 144 is disposed within the flow sleeve 142. The screen 144 isconcentrically oriented within the flow sleeve 142 and extends axiallywithin the flow sleeve 142. A first end of the screen 144 has a collar146 attached thereto (e.g., welded). The collar 146 is adapted to fitwithin a seat or pocket 113 of the first adaptor 112 coupled to thefirst flange 104. A second end of the screen 144 has a collar 148attached thereto (e.g., threaded as shown, or welded). The collar 148 isadapted to fit within the second adaptor 120 and extend through anaperture in the end cap 122. The collar 148 has a flange 149, whichabuts between surfaces of the second adaptor 120 and the end cap 122.When the end cap 122 is installed over the collar 148 and threaded ontothe second adaptor 120, the interface between the flange 149 of thecollar 148 between the second adaptor 120 and the end cap 122 preventsmovement of the screen 142 in an axial direction. Removal of the end cap122 allows the screen 142 to be removed, either for replacement orcleaning.

The screen 144 is preferably a stainless steel hollow cylindrical tubethat has a plurality of perforations to allow a fluid to enter thehollow tube and radially exit the screen through the plurality ofperforations. The screen may have an inner diameter of at least about 1inch, 2 inches, or 3 inches, up to about 4 inches, 5 inches, or 6inches. An annulus 143 is formed between an outer diameter of the screen144 and an inner diameter of the flow sleeve 142. Perforations in thescreen 144 may have a diameter of at least about ⅛ inch, ¼ inch, or ⅜inch up to about ½ inch, 9/16 inch, ⅝ inch, ¾ inch, or 1 inch. In otherembodiments, perforations in the screen 144 may have a diameter of up toabout 1½ inches, 2 inch, or 3 inches.

Further, a baffle 150 is located within the interior cavity 108 at asecond end of the main housing 102 proximate the second flange 106. Thebaffle 150 is preferably a plate welded or otherwise attached to anouter diameter of the flow sleeve 142. The plate may be at least about 1inch in thickness, and up to about 3 inches in thickness. The baffle 150is extends radially outward from the outer diameter of the flow sleeve142 towards an inner wall of the housing 102. The baffle 150 is sized tohave an outer diameter that is less than an inner diameter of thehousing 102 so that an upper passageway 152 and a lower passageway 154(e.g., gaps) are formed there between. The baffle 150 is arranged anddesigned to distribute fluid flow exiting from ports 145 a and 145 binto a larger pattern within the interior cavity 108 of the housing 102and to further separate gas from fluids.

Gas Separator Assembly

A gas separator assembly 160 is coupled to the top flow adaptor 126 byway of one or more threaded fasteners 162. The gas separator assembly160 includes a riser spool or lower body 164 having a central bore therethrough. An outlet body 166 having one or more outlets 168, both radialand longitudinal, may be coupled to the lower body 164 by way one ormore threaded fasteners 169. In certain embodiments, a blind flange 170may be disposed over at least one of the radial outlets therebydirecting fluid out remaining radial outlets 168. A tree cap 170 may befastened to the outlet body 166 by way of one or more threaded fasteners171. Finally, a threaded cap 174 having internal threads may be threadedonto external threads of the tree cap 172. Alternatively, the gasseparator assembly 160 may comprise or be formed as a single integralhousing attached to the top flow adaptor 126 of the main housing 102 andcomprising the individual components previously described in a singleintegral component.

The gas separator assembly 160 further includes a screen 178 disposedtherein. The screen 178 is preferably a stainless steel hollowcylindrical tube that has a plurality of perforations to allow a fluidto enter the hollow tube and radially exit the screen through theplurality of perforations. The screen 178 may have an outer diameter ofat least about 1 inch, 2 inches, or 3 inches, up to about 4 inches, 5inches or 6 inches. Perforations in the screen 178 may have a diameterof at least about 20 microns, 30 microns, or 40 microns, up to about 50microns, 60 microns, 70 microns or 80 microns. In other embodiments, theperforations may have a diameter up to about ⅛ inch, ¼ inch, ½ inch or 1inch.

A lower end of the screen 178 may be installed in a seat 180 attachedwithin a lower end of the lower body 164. For example, the seat 180 maybe welded within the lower body 164. An upper end of the screen 178 maycomprise a collar 182, attached to the screen 178, either welded orthreaded. The collar 182 is adapted to fit within the tree cap 172 andextend through an aperture in the threaded cap 174. Removal of thethreaded cap 174 allows the screen 178 to be removed, either forreplacement or cleaning. In certain embodiments, the collar 182 may havea needle valve 176 or the like installed therein for pressure adjustmentwithin the gas separator assembly 160.

METHODS OF USE

FIG. 2 is a simplified schematic showing the primary separator 100installed in a flowback system 5. A fracturing tree 10 (“frac tree”) isdisposed on a producing well from which a production fluid containing amixture of fracking fluids, drilled isolation plug cuttings, oil andnatural gas, water, and sand or other sediment flows. The productionfluid flows from the frac tree 10 through a fluid line 12 and enters theprimary separator 100. The primary separator 100 separates drilled plugcuttings, natural gas, and fluid and sand in a single integral primaryseparator 100.

In reference to FIGS. 1A and 1B, the production stream enters theprimary separator 100 through the inlet port 110 and flows into screen144. As the production fluid flows through the screen 144, fluids,including fracking fluids, oil and natural gas, and water, and smallersolid matter such as sand particles and similar sediment pass radiallyoutward through the plurality of perforations in the screen 144 into theannulus 143 formed between the screen 144 and flow sleeve 142. Largersolids, particularly, drilled isolation plug cuttings are caught withinthe screen 144 and prevented from passing through the plurality ofperforations. Fluid and smaller solids continue to flow either throughscreen 144 or within annulus 143 (e.g., in a swirling motion as shown inFIG. 1B) until they reach a second end of the screen assembly 140 andports 145 a and 145 b. Some separation of gas particles from the fluidsand smaller solids occurs in the annulus 143 through cyclonic separation(i.e., swirling motion), which will be understood by one of ordinaryskill in the art.

Once the swirling flow reaches a second end of the flow sleeve 142 andannulus 143, fluids and smaller solid matter within the annulus 143 flowdownward through lower port 145 b, while gas particles flow upwardthrough upper port 145 a. Fluids and smaller solid matter as well as gasparticles then encounter the flow baffle 150, which is arranged anddesigned to cause flow distribution and encourage further separation ofgas from well fluids such as oil, water, and/or fracking fluids, andsand or sediment.

Fluid and sand separation from the gas within the primary separationdevice is dependent on gravity and retention time. In certainembodiments, fluid may circulate through the primary separation deviceat a rate of between about two and three barrels per minute. In otherembodiments, fluid may circulate through the primary separation deviceat a rate of between about two and twenty barrels per minute. Onceseparated from the gas, fluids and solid matter flow downward throughthe lower port 154 of the flow baffle 150 to the liquid drain 138 at thebottom of the main housing 102. Once separated from fluids and solidmatter at the baffle, the gas flows through the upper port 152 of theflow baffle 150 to an upper portion of the main housing 102. The gasenters the gas separator assembly 160, where the gas flows into thescreen 178. As gas flows radially outward through the plurality ofperforations in the screen 178, sand and other small sediment isfiltered and remains in the screen 178. Filtered gas then exits the gasseparator assembly 160 by way of outlet 168.

As shown in FIG. 2, filtered gas exiting outlet 168 flows through a gasline 14, through a flow regulator 15 (e.g., a choke valve), and may befurther processed in a three-phase separator 16. Liquid and solid matterexiting liquid drain 138 may flow through a fluid-sand clean-up line 18to one or more deposit tanks (not shown).

Advantageously, the primary separator provides separation of drilledisolation plug cuttings, gas, and well fluids and sand in a singleassembly before said constituents reach other fluid handling equipmentnot suitable for handling such a mixture. What's more, the combinedseparation capabilities of drilled isolation plug cuttings, gas, andwell fluids and sand in a single assembly greatly reduces the footprintfor such equipment, where floor space is often at a premium.Additionally, the removable screens allow screens to be easily removedand cleaned or replaced, which increases the efficiency of theseparation process. Furthermore, once the isolation plugs are drilledand the well is being cleaned up, the primary separator described hereinmay perform as a sand trap, which may include one or more sand filtersto trap trace sand. In other words, screen 144 may be replaced in aboutten minutes or less with a sand filter having from 20 to 80 micronperforations.

What is claimed is:
 1. An apparatus for separating natural gas from aproduction stream, the apparatus comprising: a housing having a firstend, a second end and an interior cavity disposed at least partiallytherebetween; an inlet port in fluid communication with the first end ofthe housing; a flow sleeve disposed at least partially within theinterior cavity of the housing and in fluid communication with the inletport; a first screen disposed at least partially within the flow sleeveand in fluid communication with the inlet port; an annulus disposedradially between the first screen and the flow sleeve; a baffle disposedwithin the interior cavity fluidically downstream from at least aportion of the first screen; a liquid drain in fluid communication withthe interior cavity and disposed fluidically downstream from the baffle;a gas separator body extending from the housing and disposed in fluidcommunication with the interior cavity, the gas separator body having agas outlet; and a second screen disposed at least partially within thegas separator body, wherein at least a portion of the second screen isdisposed fluidically between the interior cavity of the housing and thegas outlet.
 2. The apparatus of claim 1, wherein the first screencomprises a plurality of perforations having a diameter of at leastabout ⅛ inch up to about 3 inches.
 3. The apparatus of claim 1, furthercomprising one or more ports through the flow sleeve fluidically betweenat least a portion of the first screen and the baffle.
 4. The apparatusof claim 1, wherein the second screen comprises a plurality ofperforations having a diameter of at least about 20 microns up to about1 inch.
 5. The apparatus of claim 1, wherein the baffle has an outerdiameter that is greater than an outer diameter of the flow sleeve andless than an inner diameter of the interior cavity of the housing. 6.The apparatus of claim 1, further comprising a pressure gaugefluidically coupled to the inlet port upstream of the interior cavity.7. The apparatus of claim 1, further comprising a pressure gauge coupledto the housing and configured to monitor pressure within the interiorcavity.
 8. The apparatus of claim 1, wherein the first and secondscreens are removably coupled to the housing and gas separator body,respectively.
 9. The apparatus of claim 1, further comprising a collarhaving a flange, wherein the collar is removably coupled to the secondend of the body and configured to prevent movement of the first screen.10. The apparatus of claim 1, wherein the second screen is transverse tothe first screen.
 11. The apparatus of claim 1, wherein the baffleextends radially outwardly from the flow sleeve and is disposed closerto the second end of the housing than to the first end of the housing.12. The apparatus of claim 11, further comprising one or more portsconfigured to route fluid from the flow sleeve to the interior cavity ofthe housing, wherein at least one of the one or more ports is disposedin a portion of the flow sleeve longitudinally between the baffle andthe second end of the housing.
 13. The apparatus of claim 1, furthercomprising first and second ports configured to route fluid from theflow sleeve to the interior cavity of the housing, wherein the first andsecond ports are of different sizes.
 14. The apparatus of claim 1,wherein the baffle is configured to route fluid to one or morepassageways between the baffle and an inner wall of the housing.
 15. Theapparatus of claim 1, wherein the liquid drain is disposed below theinterior cavity and the gas outlet is disposed above the interiorcavity.